PDF Toolkit

How to check whether an online PDF tool uploads your file

A two-minute test with your browser's developer tools shows whether a tool sends your document to a server.

Last updated October 10, 2026

Plenty of sites say "your files are safe". Fewer say what that means. Some upload your file, process it on a server, and delete it after an hour. Others never upload it at all. If the document is a contract, a medical record or an ID card, the difference matters, and you can check it yourself in a couple of minutes. You don't need to be technical.

What you're looking for

When a site uploads a file, your browser sends a network request carrying the file's contents, usually a POST or PUT request whose size is roughly the size of your file. A tool that works in your browser sends no such request. The browser's developer tools show every request a page makes.

The test

  1. Open the tool's page in Chrome, Edge, Firefox or Safari.
  2. Open developer tools: press F12 on Windows or Linux, or Cmd+Option+I on a Mac. (In Safari, first turn on "Show features for web developers" in Settings, then Advanced.)
  3. Click the Network tab. Click the clear button (a circle with a line through it).
  4. Choose a file in the tool and run it, just as you normally would.
  5. Look at the list. Click the Method column to sort, or type method:POST in the filter box (Chrome and Edge).

Reading the results

  • No POST or PUT requests, and nothing about the size of your file: the file wasn't uploaded. You'll still see GET requests: that's the page loading its own code.
  • A POST or PUT request about the size of your file: the file was uploaded. Click the request to see which server received it.
  • Small POST requests to analytics or ad domains: common on many sites. They usually don't contain your file, but you can click them and check the payload.

An even simpler test

Load the tool's page, then switch off Wi-Fi or mobile data, and use the tool. If it still works offline, it can't be sending your file anywhere.

On this site

Every tool here runs in your browser, and each page tells the browser to block connections to other sites. Try the test on Merge PDFs or any other tool. How it works has the details.